This invention relates to a film image reading system including a computer and a film image reader used as a peripheral device of the computer.
As a peripheral device of a computer, a film image reader is commercially available which picks up an image recorded in a frame of a 35-mm film, processes the picked up image signal into a digital data, and transfers the thus obtained digital data to the computer. Such a film image reader is provided with, as an image pickup device, a line sensor including, e.g., a CCD (Charge Coupled Device). The line sensor is slid or moved with respect to a strip of the film in a sub-scanning direction (longitudinal direction of the film) to pick up an image in each frame line by line. Then, image data reading conditions such as an exposure time are calculated based on the data obtained by pre-scanning, and the image is scanned based on the calculated conditions. During the image reading operation, the prior art film image reader controls the exposure time according to the image density of the film.
However, with the prior art film image reader, if the exposure time is too long, it takes time to output the read image from the film image reader to the computer, resulting in a reduced operability. This problem may be overcome by shortening the exposure time to a predetermined time and increasing the gain at an output or input side of the CCDs for the image in a latitude area not corresponding to the exposure time. However, in this case, the noises are amplified together with the amplitude of the CCD output. This results in a poor quality of the output image.